PIC12F675-E/P Microchip Technology Inc., PIC12F675-E/P Datasheet - Page 47

• Manufacturer Part Number: PIC12F675-E/P
• Description: 8 PIN, 1.75 KB FLASH, 64 RAM, 6 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC12F675-E/P

• A/d Inputs: 4-Channel, 10-Bit
• Comparators: 1
• Cpu Speed: 5 MIPS
• Eeprom Memory: 128 Bytes
• Input Output: 5
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 8-pin PDIP
• Programmable Memory: 1.75K Bytes
• Ram Size: 64 Bytes
• Speed: 20 MHz
• Timers: 1-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

7.2
For the A/D converter to meet its specified accuracy,
the charge holding capacitor (C
to fully charge to the input channel voltage level. The
analog input model is shown in Figure 7-3. The source
impedance (R
impedance directly affect the time required to charge
the capacitor C
impedance varies over the device voltage (V
Figure 7-3. The maximum recommended imped-
ance for analog sources is 10 kΩ. As the impedance
is decreased, the acquisition time may be decreased.
EQUATION 7-1:
FIGURE 7-3:
 2003 Microchip Technology Inc.
T
T
T
ACQ
C
ACQ
Note 1: The reference voltage (V
A/D Acquisition Requirements
2: The charge holding capacitor (C
3: The maximum recommended impedance for analog sources is 10 kΩ. This is required to meet the pin
=
=
=
=
=
=
=
=
leakage specification.
Amplifier Settling Time +
Hold Capacitor Charging Time +
Temperature Coefficient
T
2µs + T
C
- 120pF (1kΩ + 7kΩ + 10kΩ) In(0.0004885)
16.47µs
2µs + 16.47µs + [(50°C -25°C)(0.05µs/°C)
19.72µs
S
AMP
HOLD
) and the internal sampling switch (R
Legend C
HOLD
+ T
C
(R
VA
. The sampling switch (R
C
+ [(Temperature -25°C)(0.05µs/°C)]
ACQUISITION TIME
ANALOG INPUT MODEL
IC
+ T
V
I
R
SS
C
R
+ R
LEAKAGE
T
PIN
IC
HOLD
S
COFF
SS
ANx
+ R
C
5 pF
HOLD
PIN
= input capacitance
= threshold voltage
= leakage current at the pin due to
= interconnect resistance
= sampling switch
= sample/hold capacitance (from DAC)
S
) In(1/2047)
various junctions
) must be allowed
REF
) has no effect on the equation, since it cancels itself out.
HOLD
V
DD
DD
), see
V
V
) is not discharged after each conversion.
T
T
SS
SS
= 0.6V
= 0.6V
)
)
I
± 500 nA
LEAKAGE
After the analog input channel is selected (changed),
this acquisition must be done before the conversion
can be started.
To
Equation 7-1 may be used. This equation assumes
that 1/2 LSb error is used (1024 steps for the A/D).
The 1/2 LSb error is the maximum error allowed for
the A/D to meet its specified resolution.
To calculate the minimum acquisition time, T
the
(DS33023).
R
IC
≤ 1K
calculate
PICmicro™
V
SS R
Sampling
Switch
DD
6V
5V
4V
3V
2V
PIC12F629/675
SS
the
Mid-Range
Sampling Switch
5 6 7 8 9 10 11
V
minimum
SS
C
= DAC capacitance
= 120 pF
(kΩ)
HOLD
Reference
acquisition
DS41190C-page 45
ACQ
Manual
time,
, see